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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

A New Acoustic Model for Valveless Pulsejets and Its Application to Optimization Thrust

[+] Author and Article Information
F. Zheng

Department of Mechanical and Aerospace Engineering,  North Carolina State University, Campus Box 7910, Raleigh, NC 27606fzheng@ncsu.edu

R. L. Ordon, T. D. Scharton, A. V. Kuznetsov, W. L. Roberts

Department of Mechanical and Aerospace Engineering,  North Carolina State University, Campus Box 7910, Raleigh, NC 27606

J. Eng. Gas Turbines Power 130(4), 041501 (Apr 28, 2008) (9 pages) doi:10.1115/1.2900730 History: Received May 02, 2007; Revised January 07, 2008; Published April 28, 2008

Due to its simplicity, the valveless pulsejet may be an ideal low cost propulsion system. In this paper, a new acoustic model is described, which can accurately predict the operating frequency of a valveless pulsejet. Experimental and computational methods were used to investigate how the inlet and exhaust area and the freestream velocity affect the overall performance of a 50cm pulsejet. Pressure and temperature were measured at several axial locations for different fuel flow rates and different geometries. Computer simulations were performed for exactly the same geometries and fuel flow rates using a commercial CFD package (CFX ) to develop further understanding of the factors that affect the performance of a valveless pulsejet. An acoustic model was developed to predict the frequency of these valveless pulsejets. The new model treats the valveless pulsejet engine as a combination of a Helmholtz resonator and a wave tube. This new model was shown to accurately predict geometries for maximum thrust. The model was further extended to account for the effect of freestream velocity. Evidence is provided that valveless pulsejet generates the highest thrust when the inherent inlet frequency matches the inherent exhaust frequency.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Earlier pulsejet designs: (a) Marconnet and (b) Lockwood–Hiller

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Figure 2

(a) Dimensions of the experimental valveless pulsejet (in cm) and (b) pulsejet cross section showing details of fuel injection, pressure, and temperature measurements

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Figure 3

Numerical model for the pulsejet

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Figure 4

Temperature distribution along the pulsejet wall

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Figure 5

Chamber pressure and temperature at Port 3 for 1.6cm inlet diameter and 50cm exhaust duct length

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Figure 6

Frequency comparison between computational and experimental results: (a) frequency versus inlet diameter for 50cm exhaust duct pulsejet and (b) frequency versus exhaust duct length for 1.6cm inlet diameter

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Figure 7

Calculated inlet and exhaust frequency compared to pulsejet running frequency for 50cm tail pipe: (a) computational data and (b) experimental data

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Figure 8

Inlet and exit temperatures versus the inlet diameter for a 50cm exhaust duct pulsejet

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Figure 9

Temperature at the exit

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Figure 10

Thrust versus inlet diameter for 50cm exhaust duct pulsejet

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Figure 11

Thrust versus inlet diameter: (a) 42cm exhaust duct pulsejet and (b) 58cm exhaust duct pulsejet

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Figure 12

Thrust versus inlet length for 58cm exhaust duct pulsejet

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Figure 13

Chamber pressure 2.54cm inlet diameter, 0.42m exhaust duct pulsejet

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Figure 14

Thrust versus inlet diameter for different freestream speeds

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Figure 15

Thrust versus inlet diameter: (a) 30m∕s freestream and (b) 120m∕s freestream

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